Chichester were confirmed as London Four South East champions when visitors Guy's Hospital withdrew from their game.
Bognor already knew they were up before taking on Hove but still scored a 24-23 win in a highly entertaining game at Hampshire Avenue.
Skipper Karl Flynn (2), Billy Toone and Tom Spurle scored tries with Gareth Williams and Stuart Pearce adding one conversion apiece.
Flynn passed up the chance to kick easy penalties and thought he was going to be punished when Andy Standing scored a late try for Hove, but Martin Lovell was off target with the conversion attempt.
The Bognor captain said: "We have done really well to go up having looked out of it around Christmas.
"We really wanted to go out in style and it was a cracking game."
The result leaves Hove needing a point at home to Chichester in their final game to be sure of staying up.
Joe Carpenter and Dom Henderson scored their other tries with Lovell adding a conversion and two penalties.
Crawley rested players struggling with injuries and lost 28-9 in a high-tempo affair at Folkestone. Andy Evans kicked three penalties.
Heathfield skipper James Dimmack returned after a four-month injury lay-off in the 34-24 home defeat by Bromley.
Tim Evans (2), Brady Burdett and Julian Wates scored Heath's tries in a spirited display.
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